Understanding the needs for super smooth optics give insights for optical fabricators tasked to produce them. These needs include substrates for metrology and a host of X-ray applications. In addition to some grazing angle of incidence optics, normal incidence optics with multilayer stacks have been recently produced. These optics have very demanding finish requirements. Lacquer and flow polishing have produced some interesting surfaces.

Developments in 2 axis CNC aspheric machines and aspheric measuring instruments met the growing demand for high accuracy aspheric form machining, machine and machining accuracy have significantly improved in last 6 years. It was found that spherical form could be machined and measured to a very high form accuracy, which was not possible to match for aspheric form due to the measurement term of absolute radius with form accuracy. Form correction software for use with aspheric form measuring instrument (Form Ta.Iysurf) was developed by Rank Taylor Hobson (RTH) to eliminate waviness on the diamond cutting edge and radius error from true radius and to reduce aspheric form machining accuracy down to that of spherical form.

The study of microscopes for shortwave light such as X rays has made much progress in recent years. Accordingly, the demand for a super-smooth aspherical optical element is increasing. The purpose of this research is to achieve a 0.08 p m or less surface figure error (relative accuracy 1O),and a 0.2 nm rms or less surface roughness on freeform surface optical elements of 500 mm in diameter or more. In order to improve the degree of surface roughness, we used a local pitch polishing method that had a profile generation possibility. A surface roughness of less than O.O6nm rms was achieved in the end of 1990 using the fused silica. In order to improve figure accuracy and ripple, we developed the Canon Super Smooth Polisher (CSSP)(Fig.1) which corrects the figure error by an on-machine measurement and developed a profile generating algorithm by early 1991. In this paper, we describe the results of studies on super-smooth polishing methods and the evaluation results of the CSSP system.

As optica' tecimology has been improved in recent years, devekpment of large sca'e and high precision optics is atso required. For measuring these optics, a non-contact form measuring probe, with nanometer order reso'ution and a 10 pin measurement range, has been developed. The probe has been installed on the work tab'e of an ulira precision CNC machine whose X— and Z-axis tables are positioned by a laser interferometer system with 2.5 nm resolution. The probe has measured deviations between the ideal surface form and the machined surface form. By using this system, form accuracy of large sca'e workpieces, such as high precision mirrors over 300 mm diameter, could be measured with high accuracy better than 0.1 pin.

We have developed a new method of injection molding (GATESEALTN injection molding method) for ultra-precise plastic lenses. Our method is summarized as follows: 1) The filling pressure is selected to make the pressure of the polymer the same as the atmospheric pressure at opening the mold, and the mold temperature at injection is higher than the glass transition temperature (Tg); 2) After injection filling and sealing the gate, the pressure and temperature of the polymer in the cavity are homogenized by keeping the temperature of the mold constant at above Tg; 3) The mold is gradually cooled down below the heat distortion temperature without any change in specific volume. The surface figure accuracy is a peak—to-valley roughness better than 0.3 im and a root mean square roughness better than 0.04 pm. The unique feature of our method is to control the temperature of the mold after injecting a constant weight of polymer into the cavity of constant volume. We are now mass—producing a wide range of thermoplastic lenses for optical systems by this new injection molding method.

From the option's viewpoint, aspheric surfaces are usually the most difficult surfaces to fabricate accurately. For this reason, the cost of aspheric elements which are figured by hand is high. In this paper, a computer controlled generation of rotation— ally symmetric aspheric surfaces is presented, which accurately predicts material removal rates with a X—Y type computer—controlled polishing system and a small polishing tool. In according to theoretical calculation,300mm spheric surface (r=2090) is figured into a 300mm f/3.5 parabolic surface along 10 concentric circle areas in 30.8 hrs. The surface accuracy of A./8(RMS) can be obtained,by testing tower including CQG—1 digital interferometer. After analysis of the technique methods and experiment results, we come to the conclusion that the double rotation tool polishing removal profile is the key parame— ter,To insure the optical surface quality, the different polishing paths, optimized operating parameters and adequate detecting system are required in polishing of different aspheric surfaces. A computer model of the polishing process was developed and used to investigate the removal profile of various tool shapes and different polishing parameters from the model. Software was developed to control the X—Y stepmotors, monitor the process, calculating material removal profiles and surface testing data. Some unsolved problems and other possible uses are discussed in this CCP system. Finally, the development of the X—Y polishing machine and the necessary software of IBM/PC microcomputer to implement the process are also discussed.

The optical components processing and measuring techniques started late in China, but they have been made great progresses in recent years. Their development situation is reviewed here. The present situation on precise, aspherical and tiny processing and measuring techniques is also introduced. In this paper,we emphatically discuss the high—efficiency processing of optical components. Finally, approximation on development direction is given.

The accurate measurement of surface finish requires standard specimens to calibrate and check the operation of the measuring instruments. This is true both for profiling techniques such as the stylus and area averaging techniques such as light scattering. For profiling stylus instruments, the international standard ISO 5436 has enumerated four types of standard specimens which may be classified as step height specimens, periodic roughness specimens, random roughness specimens, and specimens for checking probe tip resolution. A draft of a related U.S. standard uses the same taxonomy. For light scattering instruments, the use of standard specimens are discussed in the ASTM standard for total integrated scatter. In addition, several ad hoc standard specimens have been used in an interlaboratory comparison of instruments that measure the bidirectional reflectance distribution function (BRDF). Our group has developed a series of specimens, known as standard reference materials (SRMs), for calibrating stylus profiling instruments. We are also in the process of developing a series of profile specimens for calibrating the linearity of BRDF instruments. Both types of specimens have sinusoidal profiles and are discussed in turn.

A new method to measure the surface roughness under a fully developed speckle pattern illumination has been proposed. This technique is used on the basis that the roughness depends on the speckle size of doubly scattered light and the size can be determined from the spatial fluctuations of the integrated intensity over a finite area. Using the CCD camera as a photodetector, the proposed system can determine the roughness at on-line.

A useful and excellent method to measure the surface roughness in a real time has been proposed and investigated. In the method, the real-time Fourier transformation of doubly scattered speckle pattern is used.

This paper discusses some non-contact measuring methods of optical surface roughness. Three types of optical interference profilometers researched in China are mentioned. Some unique techniques used in them are introduced. The advantages and disadvantages of them for on-line measuring are discussed.

Recent advances in aspheric technology have resulted in remarkable progress in the manufacture of compact zoom lenses for consumer use such as photographic cameras or video cameras. The aspheric technology consists of aspheric lens production technology and also aspheric lens design technology. The author discusses recent advances in the above technologies and typical examples of zoom lenses which are successfully commercialized as aspheric zoom solutions.

The surface topography of various samples has been measured using an optical profiler and a scanning probe microscope (SPM). Optical profilers offer fast and accurate measurements of surface topography but are limited in their lateral resolution by the wavelength of light used. SPMs extend the lateral resolution down to atomic dimensions. Topography measurements are used to obtain surface roughness data. We find that for a scan size of 50 X 50 micrometers , the roughness data obtained from the optical profiler agree with the SPM measurements. The roughness data do not vary significantly when higher magnification images are taken with the SPM on surfaces that lack high frequency components. But for surfaces that have rough features that are smaller than the resolution of the optical profiler, roughness data calculated from higher magnification images by SPM can vary significantly.

This article describes surface roughness and waviness measurements for optical parts. The basic description of roughness is reviewed for a digital surface profiler and comparisons made for the lower spectrum description of surface topography. The power spectrum analysis is also reviewed with a special emphasis on a low variance algorithm. Applications for the optics industry for both flat and curved parts are presented.

A new fringe-scanning microscope based on a coherence probe microscope is described for measuring both the surface profile and the local material of a heterogeneous sample in nanometer depth resolution. The basic configuration is a white-light double-beam interferometer with either a Michelson or Mirau objective lens. The sample stage is moved down during the measurement and an interference image is collected at every stage-height. The surface profile is reconstructed in the computer by tracing the darkest point of the white- light interferogram for each pixel. The surface material is identified pixel by pixel by calculating the amplitude and the phase reflectivity of the spectrum by Fourier transforming a local interferogram or taking a cross-correlation of it with reference ones. Experimental examples of surface profile reconstruction, including a sample with film on it, are shown. An experimental result of local material identification is also presented.

Interferometers have come to be used in production processes for surface profiling. Common- path interferometers are becoming important because they are insensitive to environmental disturbances such as mechanical vibration, air turbulence, and thermal drift. Among common- path interferometers, those using double-focus lens are promising because they can easily incorporate phase-shifting technique. In this paper, common-path interferometers using double-focus lenses are described and some experimental results are given. Properties of double focus lenses are investigated and their effect on surface profiling is discussed.

A scattering measurement apparatus equipped with a halogen lamp and an integrating sphere was constructed. The scattering characteristics of ZrO2/SiO2 multilayers were measured in the visible region. The scattering characteristics did not only follow (lambda) -4 relation but also depended on the optical characteristics. It was shown that the electric field intensity distributions qualitatively explained the scattering characteristics. Also, the apparatus was useful as an instrument to find out the optimum deposition conditions of multilayers.

This paper describes the principle of the space datum line obtained by a paralleled plate. When the paralleled plate is a wedged one, the paper gives not only the distribution of the image points via many times of refraction and reflection inside the plate, but also the deviation compared with the datum line.

In modern optical industry and optical research the anisotropic crystals, such as iceland, KDP, ADP, LiNbO3, crystalline quartz, etc., have been widely used for making various types of polarizers, optical shutters, interference polarization filters, and light modulators, etc. In order to improve the quality of crystal elements, the accuracy of crystal optical axis orientation must be improved. In this paper a new type of instrument is described for determining the perpendicular orientation of the crystal optical axis of a crystal plate to the plate surface. A converging bundle of polarized rays passes through the plate and forms a set of ring interferogram and a dark cross image in the interferogram. As the working stage is rotated, the center of the cross and the rings move along a circle, if the surface of the plate is not perpendicular to the optical axis. The accuracy of data read directly from a beeswax screen of (phi) 150 mm does not exceed six arc minutes. If the data and other parameters are input to a microcomputer IBM/PC to remove the theoretical deviations of the instrument the accuracy of two arc minutes can be obtained. The size of crystal under test can be (phi) 100 X (0.5 - 100) mm. Theoretical calculation shows that the accuracy of a thick crystal plate under test and the data read from an interferential ring of lower order of interference are improved. In this instrument the crystal cone interferogram, clean and bright, is projected on a screen, and it is suitable for teaching demonstration and shop testing. The cost of this instrument is lower because of its simple structure.

Some results obtained as part of a multilaboratory research project entitled `x-ray imaging optics' are presented, with emphasis on a new generation of optical components and systems designed to operate in the soft x-ray (SXR) region. Included are discussions of optical constants for various thin-film materials in the SXR region, SXR multilayers, SXR microscopes, x-ray telescopes, and metrological instrumentation for testing and characterizing SXR optical elements.

The structure, and therefore the performance, of multilayer x-ray mirrors is directly related to the growth mode of the constituent materials. We review some of our recent results from using molecular beam epitaxy (MBE) for the growth and study of materials for x-ray optics. This work involves the study of surfaces and interfaces important to improving conventional multilayer mirrors and development of superlattice mirrors. Recently, we have successfully grown hcp (0001) Be epitaxially on (0001) (alpha) -Al2O3 substrates. We find the orientation and morphology are strongly influenced by the substrate temperature during deposition. The discovery of a technique to grow Be epitaxially, coupled with the favorable optical constants of this material, gives Be-based multilayers great potential for the development of superlattice x-ray optics. In our preliminary studies of Be/Ge multilayers we found them to have a layered structure, making Be/Ge a potentially useful combination for soft x-ray mirrors. In another series of studies, we performed investigations of film growth and interface formation using a variety of surface analysis techniques for Mo on Si and for X on B (where X equals Pd, Ag, Si). These studies were carried out by depositing onto clean surfaces in ultra high vacuum, followed by characterization with in situ reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and ex situ by scanning tunneling microscopy (STM) and x-ray diffraction. Continuous growth of multiple coverages on a single substrate was accomplished with a technique involving a moveable sample shutter. For Mo-Si, our data are consistent with a composition profile that has an atomically abrupt transition between Si and amorphous MoSix, where x equals 2 for the first 4 angstroms. The fraction of Si then decreases, with the composition approaching pure Mo after 15 - 20 angstroms depending upon the growth temperature. This silicide interlayer causes only a small reduction in the reflectivity of Mo/Si soft x-ray mirrors with (Lambda) > 60 angstroms, but has severe effects for smaller period structures. For Ag-B, the XPS, AES, and STM data are all characteristic of an island (three-dimensional) growth mode. At an Ag coverage 15 angstroms, the islands range in height from 100 to 200 angstroms and are 2000 to 3000 angstroms across. Although the interface between Ag and B may be sharp, the island growth mode causes too much roughness for the multilayers to be useful for short-wavelength optics. For Pd-B, the Pd reacts with the B to form an amorphous, Pd-rich boride. Although the absorber layer is an alloy, our calculations indicate that the ideal normal-incidence reflectivity of the reacted multilayers could be as high as 51% at 80 angstroms. For Si on B, the interface is quite sharp and the amorphous Si forms a smooth continuous layer. Si/B multilayers are useful as narrow bandpass mirrors for (lambda) > 125 angstroms.

Material pairs of Re/Al, Re/Mg, Re/B, Pt/B, and Pt/C were selected for grazing incidence multilayer mirrors having a high reflectance for about 1 nm wavelength x ray. The multilayers were fabricated by electron beam deposition and Knudsen cell heating deposition, and were evaluated as to whether or not they had a periodic structure and stability in atmospheric storage. A periodic structure was observed in the transmission electron micrograph for the Pt/C and the Re/B multilayers, although the Re/B multilayer was found to have a decay after a month of fabrication. This decay was caused by the formation of an Re oxide as judged from the x-ray photoelectron spectroscopy analysis.

We have selected Cr and C as a material pair of multilayer (ML) mirrors for soft x rays at the wavelength near 5 nm. The Cr-C ML structures have successfully been fabricated with rf- magnetron sputtering. The ML structures have been characterized with transmission electron microscopy (TEM), x-ray diffraction, and reflectivity measurement by SR light. From the observation of TEM images, Cr-C MLs had uniform and less-defective layered structures with the d-spacing down to 2.4 nm. Reflectivities at normal and grazing incidence were remarkably decreased with decreasing the ML d-spacing. Normal incidence reflectivity at 5 nm was as high as 7%. The regularity of the d-spacing of the MLs was evaluated with a moire image that was formed by putting a reference stripe pattern on the cross-sectional TEM micrograph. Compared to Ni-C MLs, Cr-C is a preferable material combination for x-ray mirrors for shorter wavelength and normal incidence.

The design of the Schwarzschild objective considering an alignment error is discussed and its fabrication for a soft x-ray microscope is described. It is shown that performance degradation of a Schwarzschild objective by an alignment error can be reduced in a heterocentric system, in which the center of a curvature of a concave mirror is not coincident with that of a convex mirror. Objectives with a magnification of 100 and 224 have been fabricated. To complete an indispensable and difficult alignment within the objective itself, the two mirrors are mounted together in the same frame. The alignment errors of the mirrors are detected and their positions are corrected in a newly developed alignment system, which allows the alignment to achieve the tolerance of 0.3 micrometers . The fabrication of Mo/Si multilayers used for the mirrors are also described briefly. A reflectometer using a laser produced plasma source has been developed to measure reflectances of multilayers. The Mo/Si multilayer deposited by magnetron sputtering shows a reflectance over 40% at a wavelength of roughly 135 angstroms.

We have successfully demonstrated double pass enhancement of amplified spontaneous emission of soft x rays, 23.2 and 23.6 nm of 3p - 3s transitions in Ne-like Ge, using an x-ray multilayer mirror. In this paper, we report on the fabrication of the mirror and analysis of its damage suffered during the experiments. The mirror used was a Mo-Si multilayer mirror with the reflectivity of 35% at the wavelength of 23.6 nm, deposited by an rf-sputtering system. In the damaged area of the mirror, only the multilayer was locally evaporated and the bare substrate underneath appeared. The size of the damaged area corresponded to the aperture size. We carried out the simulation on the spatial and temporal distribution of the mirror temperature during the experiment. Assuming that thermal x rays enter the mirror with the largest amount of energy among all the fluxes at the early stage of the enhancement, the result of the simulation can explain the damage feature and the temporal profile of the intensity of the amplified spontaneous emissions.

Improved x-ray mirrors for synchrotron radiation (SR) lithography have been developed and installed in our beamlines. The optimum grazing angle of a platinum (Pt) coated mirror which effectively converges SR beams is derived. The surface roughness of the Pt films is measured by using an optical surface profiler, an STM, and x-ray reflectivity measurements. It is found that x-ray reflectivity strongly depends on the surface micro structure. Improved vacuum evaporation and ECR sputtering are used to coat Pt film on the mirror surfaces. Using the improved vacuum evaporation film, the surface roughness is 1 nm and reflectivity is 50% at a 1.8 degree grazing angle, at a 8.34 A wavelength. Using the ECR sputtering film, surface roughness is below 0.3 nm and reflectivity is above 60%. A two-toroidal mirror device is used to increase the x-ray intensity on the wafer and to vertically expand the exposure area. Astigmatism is intentionally introduced in these mirrors to increase their converging and collimating abilities. A divergence angle of 2 degrees and an exposure area of 25 X 25 mm2 are obtained by using Pt-coated astigmatic toroidal mirrors. The resulting x-ray intensity on the wafer is 0.05 mW/cm2/mA and the peak wavelength is about 7 to 8 A.

The optical constants, (delta) equals 1 - n and k, of very thin platinum, rhodium, and gold films have been determined from the reflectance data measured in the soft x-ray region of 60 - 900 eV. Five platinum films (63 - 153 angstroms in thickness), five rhodium films (53 - 124 angstroms), and nine gold films (49 - 270 angstroms) were prepared by ion-beam sputtering on BK7 glass substrates. A Debye-Waller factor was applied to the Fresnel reflectance to take into account the reflectance degradation due to the roughness in the surface and the interface in the least-squares curve fitting analysis. The optical constants determined for the platinum and rhodium films show little dependence on the film thickness, while those of the gold films show definite dependence in a thickness range of 70 - 120 angstroms.

An x-ray mirror system based on the off-axis configuration of Wolter-type mirrors is built up for microscopic x-ray photoelectron spectroscopy ((mu) -XPS), and its focusing characteristics are evaluated using the MgK(alpha) x rays (1253.6 eV). The focussed beam diameter is 15 - 20 micrometers when the 6 mm diameter x-ray source is used. This indicates that the mirror system has achieved the high demagnification of 1/300 - 1/400 required for (mu) - XPS analysis in the micrometer range. The future performance of (mu) -XPS analysis using a rotating-anode x-ray source is outlined.

Soft X-ray microscopy, especially using the wavelength region from 2.4nxn to 4.4nxn, is expected in biology. Because the microstructure of live and thick biological specimens containing water can be observed by x-ray absorption difference of protein and water with low damage. The final goal of this work is to produce an imaging x-ray microscope for biological studies.

Diamond-cut flat mirrors with controlled surface roughness are evaluated by measuring the angular distributions of x-ray scattering in the hard x-ray region (1 Angstrom). The reflection profile, for a glancing angle of 1 mrad, has a sharp peak with a FWHM of less than 10 (mu) rad. This has a potential application to a hard x-ray microprobe with a sub-micrometers spot. The reflection profile includes subpeaks due to surface undulations of about a 6 mm period equal to the ball screw lead of the cutting machine. However, small pitches in the surface roughness, such as the tool feed (15 micrometers ), do not affect the peak profile of the reflection beam, because the diffraction angle is detected at more than 1 mrad away from the specular reflection angle.

The Japan national large telescope (JNLT) project challenges new technology in adopting an actively supported monolithic 8 m mirror of meniscus form with a thickness of 20 cm. An air- flow-controlled co-rotating telescope enclosure is designed to protect the sensitive main mirror from disturbing wind, yet to keep enough flushing effect, in order to achieve the high image resolution target of approximately 0.'2.

The aspherical plastic singlet which we developed in 1984 is widely used not only for CD (Compact Disc) players, but also for every sort of optical disk player and driver. The history, the development technologies, the impact of the development and its fringe effects, as well as the recent progress, and a forecast for this aspherical plastic singlet are summarized.

A new computer generated hologram (CGH) zone-plate common path interferometer which can be used for testing an aspherical mirror with large aperture is presented. A CGH zone- plate made by laser beam drawing is used as the null optical element and its diffraction of (0, 0) and (+1, +1) orders are used as reference light and test light, respectively. Therefore, stigmatic points can be formed so as to use spatial filter effectively to get rid of extraneous light. As a result, fringes with high S/N can be obtained.

The zone-plate interference fringe pattern is analyzed by FFT. The spectrum obtained by FFT contains information on the shape error. To select the information on the shape error from the spectrum of the fringe pattern is difficult, because the resolution of the spectrum is low. An FFT with over-sampling is applied to increase the spectrum resolution. A method is proposed to select the necessary information from the spectrum of the fringe pattern. Experimental results obtained by the proposed method agree well with those obtained by Fizeau interferometer.

Fringe scanning for analyzing shape error of a test surface is performed by fringe shift of interference images with different phases. The method of proposed fringe shift is carried out by a zone-plate, which has fan-shaped sections of four different initial phases of 0, (pi) /4, (pi) /2, and 3(pi) /4. Experimental results agree with the theory.

Polarization elements at present are inadequately characterized for many applications. For retarders, usually only the retardance is specified. For polarizers, usually only the two principal transmittances or the extinction ratio are given. For polarization elements used in critical applications, this level of characterization is woefully inadequate. Defects of polarization elements are described, and appropriate performance measures suggested. Examples of the characterization of polarization elements as a function of angle of incidence, and as a function of wavelength are provided.

We propose a two-dimensional birefringence measurement method. A linearly polarized light goes through a Babinet-Soleil compensator whose principle axis direction is set 45 degree to the incident light. The light is affected by the birefringence when it passes through an optical sample. The interference fringe behind a linear polarizer is captured wholly as a two- dimensional image by a CCD camera. The data is analyzed into the phase information by the phase shifting technique using a Babinet-Soleil compensator. Here the obtained phase changes sinusoidally. Its amplitude and phase mean the relative retardation and azimuth angle respectively when a polarization azimuth of the incident light is rotated. A half-wave plate as a phase shifter is used again to obtain this amplitude and phase using the phase shifting technique again. We discuss these experimental procedures and results applied to such optical components as a lens and a roof prism.

A novel method for contour-mapping principal stress distributions is described. In the polarimeter developed, a reference beam of light consists of the two orthogonal linearly polarized components that interfere with their counterpart orthogonal components of an elliptically polarized signal beam of light. Two crossed interference patterns are formed over a MOS TV camera so that the significant parameters for determining a principal stress distribution can be recorded in a computer. The major advantage is that not only each of the two principal stresses but also the principal stress-difference can be independently determined, and no use of any optical component for polarization alignment makes it possible to follow a rapid change in stress distribution within the maximum frame rate 2066 s-1 of the MOS TV camera.

A new measuring method of 2-D birefringence distribution has been developed. It has not been an easy job to get a birefringence distribution in an optical element with conventional ellipsometry because of its lack of scanning means. Finding an analogy between the rotating analyzer method in ellipsometry and the phase-shifting method in recently developed digital interferometry, we have applied the phase-shifting algorithm to ellipsometry, and have developed a new method that makes the measurement of 2-D birefringence distribution easy and possible. The system contains few moving parts, assuring reliability, and measures a large area of a sample at one time, making the measuring time very short.

In this paper , the adhesive of the thin film on optical glass is discussed . The undulation of the polishing surface has a great influence upon the adhesive of the thin film, the undulation is due to the surface glass flowing again . We compared the adhesive of the thin on the three kind of polishing surfaces , in order to prove our view.

A float polishing method used for final polishing of a cylindrical grazing incident x-ray telescope component is described in this paper. The workpiece is initially made by a diamond turning machine. A small polisher moves along the axis of the component to be worked. Dwell time and stroke length in different position of the component are controlled by the error contour of the component given by the measurement. The polisher is made in a special way and has good flexibility to match the curvature change of different portions of the component to be fabricated and has enough hardness to keep the efficiency of the polishing process. The polisher is immersed into the aluminum oxide solution diluted by distilled water with 9 - 11 PH. The conditions and parameters of the polishing process are given in the paper. The shape of the mirror is checked by a narrow block of sphere master which contacts with the workpiece at four points of two ends of the component. A computer program is written for calculating ideal distribution of interferometric pattern and for treating real pattern formed between the master and the workpiece to give the error of the component. The roughness, which is higher than 1.5 nm rms has been reached by this method, the roundness of the component is less than 40 nm and the error of the form of the component is about 150 nm. Modulation transfer function (MTF) of the final assembly is measured with visible light to make sure that the telescope has correct assembly and the result is given in the paper.

A laboratory reflectometer with a laser produced plasma source and a constant deviation angle monochromator is used as an ellipsometer to evaluate a transmission multilayer phase shifter. With use of the phase shifter, all normalized Stokes parameters of the incident beam to the reflectometer from the monochromator were measured.

Soft-x-ray transmission multilayers have been designed and fabricated for use as polarizing elements. Polarization performance of the multilayers has been studied at a photon energy of 97 eV by rotating analyzer ellipsometry with a multilayer reflection polarizer. The transmission multilayers were found to be a good polarizer of 99.2% polarizance and a phase shifter of 90 degree(s) retardation with equal transmission ratio (5:3) and high throughput around 10%.

With respect to the cases of observing the wavefronts passing through a lens, studies were made for improving the fringe contrast from both aspects, temporal coherence and spatial coherence, of the light sources of interferometers. Experiments based on the studies also were done, employing an excimer laser and a projection lens as the light source of a Twyman-Green interferometer and the lens under test, respectively, which the experiments showed had preferable results. There is, however, a possible problem which could occur if the lens under test is not corrected for chromatic aberration.

As a modified heterodyne interferometer the heterodyne common path interferometer for measuring surface roughness is described. The interferometer system adopts the isosceles triangle type common path interferometer in which the reference beam and the measurement beam pass through the same optical path so that the mechanical instability, air turbulence, and temperature variations will affect the same value of the optical path for both the beams. The actual height resolution is 1 angstrom, and the lateral resolution is 1 micrometers . This modified interferometer can use general He-Ne laser which needs no frequency stabilizer and general experimental stage without shockproof.

Phase-measurement interferometry (PMI) techniques enable quantitative measurements to be performed in optical testing, holographic interferometry, and speckle metrology. This paper presents the results of error analyses of the most common errors in phase-measurement techniques. These errors include miscalibrated and nonlinear phase shifters, detector nonlinearities, detection quantization, vibration and air turbulence, and frequency mixing. Simulations providing the magnitude and form of these errors are shown for a number of different phase-measurement algorithms.

A sample consisting of different metals in the same plane is fabricated, and its surface profile is measured by interferometry. In spite of the flat surface, a virtual step height (max. value equals 33 nm) is measured at the boundary of the two adjacent metals. The measured step height corresponds to the difference in the phase change of reflected light between the two metals. From the results, the effect of the phase change on surface profilometry is estimated.

It is difficult to measure the optical surface shape of large area plane using interferometers. A part of the area of the sample is measured repeatedly by using a small aperture interferometer. The connection of the adjacent areas data is made with the aid of the least square method. This paper shows a method of connection of the measurement and shows some results of experiment.

Interferometers always measure the relative phase distribution of a sample to a reference subject, and absolute measurement of the sample is difficult unless the exact shape of the reference phase distribution is known. A method of differential interferometer, in which the differences of two interferograms obtained before and after the slight change of parameters in the optical configuration is measured, can be used to measure the shape of the sample without the exact knowledge of the reference phase distribution. This method is applied for measuring the radius of curvature of a Newton gauge.

Research at Carl Zeiss has led to some innovative solutions in the field of optical test methods and interferometry. One example is the method of `direct measuring interferometry' (DMI), which was developed to overcome the problems of vibration and air turbulence when testing big astronomical primaries and is now the heart of the Carl Zeiss laser-interferometer DIRECT 100. Since DMI offers real-time capabilities for the wavefront evaluation, a built-in frame-memory can act as an `electronic hologram' and opens very elegant ways for in-situ correction of small residual errors, for easy aspherical testing, a very simple way of two- wavelength-interferometry, or a new discipline of time-resolved interferometry.

A two-wavelength laser-diode (LD) interferometer has been constructed that is based on a phase-shifting technique with an electronic calibration. The phases are equally shifted in opposite directions to each other on an unbalanced interferometer using two wavelengths changed stepwise by separately varying the currents in dual LDs. A feedback interferometer is described with electronics to calibrate the phase shifts and to lock the interferometer on a phase-shift condition by controlling the bias and modulation currents of both LDs. The experimental result is shown to measure a diffraction grating with a 4.6 micrometers synthetic wavelength.

An oblique incidence interferometer for measuring a non-optical surface of a gear tooth with a phase shifting method is developed. The incidence angle of a He-Ne laser is set to be 84.75 degree(s) with a wedge prism, to obtain fringe spacing corresponding to the height of 3.64 micrometers . The reference beam is piezo-electrically modulated to make phase shifting fringe analysis. A high resolution CCD camera with resolution of 1280 X 1024 is used so that about 200 fringes can be analyzed. The maximum deviation of about 420 micrometers from a plane reference surface is measured with an accuracy of 40 nm.

A 3-D profiling system has been set up utilizing grating's self-imaging effects and one step phase-shift algorithms. In the system, the self-image of a linear grating is projected on a tested diffuse surface without any imaging lens, and then a phase deformed grating is generated on the surface corresponding to its shape. Arranging the deformed pattern to be imaged by a CCD camera at the magnification of 4 pixels per fringe period, the phases produced by surface shape can be extracted by arc tangent calculations with only one frame of fringe picture. An advanced phase ordered unwrapping algorithm, which can minimize the propagation of errors, is adopted for phase connections of 2(pi) jumps. We got the rms accuracy of 2(pi) /35 from 256 X 256 point phase measurements under 0.5 mW He-Ne laser illumination.

A surface height variation measurement device based on the differential heterodyne interferometric scheme using new optical beam scanning techniques is described. An acousto- optic deflector (AOD) is driven by a signal which has two frequency components to generate two first-order diffraction beams at different frequencies for the probing light beams. The two beams, which have only a slight separation, are deflected by the AOD. The scanning distance of the two beams via the AOD can be extended using a Galvano mirror, which is driven synchronized with the AOD and scans the two beams in the same direction. The scanning direction of the two beams can be changed in various directions in the two-dimensional plane using a specially made rotating prism. The difference in surface height between the points where the two beams are incident is detected from the phase change of a beat signal with accuracies on the order of 1 nm. We applied this device to surface condition measurements, such as surface roughness, shape, and fine angle.

Two holographic methods suited for the measurement of flatness deviation are presented. The first one takes advantage of the basic holographic interferometry arrangement usually meant for deformation analysis of rough bodies. Simple modifications allow flatness measurement of polished surfaces with sub-wavelength sensitivity. Secondly, a new desensitized interferometer is described allowing the measurement of rougher objects, more frequently encountered in engineering practice. The key component of this interferometer is a diffractive optical element produced by recording two wave interference patterns. Desensitization factors ranging from 1 to 100 with respect to a Fizeau interferometer can be achieved. Flatness checks of computer disks demonstrate the possibilities of both interferometers. Deformation measurements performed with the desensitized interferometer are presented.